Disc drives are used for data storage in modern electronic products ranging from digital cameras to computer systems and networks. Typically, a disc drive includes a mechanical portion, or head disc assembly (HDA), and electronics in the form of a printed circuit board assembly (PCB), mounted to an outer surface of the HDA.
The PCB controls HDA functions and provides an interface between the disc drive and its host. Generally, the HDA comprises one or more magnetic discs affixed to a spindle motor assembly for rotation at a constant speed, an actuator assembly supporting an array of read/write heads that traverse generally concentric data tracks radially spaced across the disc surfaces and a voice coil motor (VCM) providing rotational motion to the actuator assembly.
During use, each of the read/write heads is supported by an air bearing that is created by the rapid rotation of the adjacent disc. One approach taken by disc drive manufacturers to increase recording density is through reduction of the fly height of the read/write heads. Reducing the fly height of the read/write heads decreases the surface area each occupied by data, thereby increasing number of bits capable of being stored on the surface area of the disc. As discussed below, however, a reduction in fly height may frustrate efforts to launch the read/write heads from a parked position into flight.
When the disc drive is not in use, the read/write heads are typically landed and brought to rest in a landing zone, which is generally located near the inner diameter of the recording surface. In landing the read/write head, the read/write head is flown over the landing zone and the rotation of the spindle motor is gradually stopped. Once the read/write heads are “parked” in the landing zone, it is advantageous to secure the actuator assembly with a latching arrangement to prevent the read/write head from subsequently moving out onto the data storage zone of the disc while the disc drive is non-operational.
In most applications, the landing zone has a textured surface to mitigate a phenomenon referred to as “stiction,” which is an adhesion of the read/write head to the rotatable disc surface as a result of two smooth surfaces coming in contact with each. One method of providing this non-smooth surface is to texturize the landing zone using a laser beam. The laser beam is held at an energy output level sufficient cause a plurality of minute eruptions that form a plurality of peaks and pits on the otherwise smooth rotatable disc surface. The result of the process is a laser-textured landing zone.
Subsequent to the texturing process, a carbon overcoat is applied to the surface of the disc. The carbon overcoat serves as a wear surface between the read/write head and the magnetic recording layer of the disc. Breakdown of a carbon overcoat leads to corrosion of the magnetic recording layer, which can eventually render the entire rotatable disc surface inoperable as a magnetic storage medium.
The height of the peaks in the textured landing zone is typically controlled to be no greater than a nominal fly height of read/write head. Therefore, as fly heights of the read/write heads decrease, the height of the peaks should also decrease. The decrease in height of the peaks decreases the efficacy of the landing zone in mitigating stiction. An increase in stiction between the read/write head and the landing zone results in extended contact time between the read/write head and the surface of the disc. The extended contact time accelerates wear of the carbon overcoat, which reduces the operating life of the disc drive.
There is therefore a continued need for improvements in the art directed to reducing and dispersing wear caused by contact between read/write head and a rotatable disc surface to extend the operating life of a disc drive.